Ford Probe Idle speed with A/C engaged

JLHAWKINS on Sun August 03, 2008 10:35 PM

I have a '95 Ford Probe, 2.0L, manual transmission that has been in the family about 10 years. The problem I am experiencing is idle speed with the A/C unit engaged. When the A/C is engaged, the compressor engages, the cooling fan runs and the system cools very well. The problem is the idle speed. Normal idle speed without the A/C load is approximately 750 RPM. When the A/C is engaged, this speed drops to about 500 RPM. The engine does not die but is in labor due to the A/C load. With the A/C load, the engine freely revs and like I stated before, the A/C cools very well. In fact, I have not had to add any refrigerant nor open the system during the entire time we have owned the vehicle.

I have checked the ISC valve and the resistance on the coil is the correct value. I have a Chilton manual on the vehicle but it does not go into much detail on the idle speed control. Has anyone else had experience with this type problem on this type vehicle or could someone explain exactly how the idle speed is increased to compensate for the compressor load on this vehicle? The Ford Probe and the Mazda MX-6 are identical vehicles, just different sheet metal.

Any assistance with this problem would be greatly appreciated.

Thanks

JJM on Mon August 04, 2008 2:36 AM

Is a scan tool showing the A/C on signal to the PCM? If your scan tool isn't that detailed, if the compressor kicks out at WOT, chances are the PCM is getting the A/C on signal.

How long has it been since you cleaned the throttle body? If it was more than 30,000 miles ago, it's probably time. Clean the throttle body THOROUGHLY, run the engine to burn up the solvent, and once the engine is running smoothly, shut it down, disconnect the negative battery cable for about a minute, reconnect and restart the engine for the relearn process.

Joe

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